This project is concerned primarily with the physiology of vertebrate photoreceptors, the processing of visual information within the retina, and the mechanisms underlying retinal responses. Both intra- and extracellular recordings will be made from photoreceptors and retinal neurons in selected species. Specific problems currently under investigation include: 1) The role of potassium in modulating retinal sensitivity in the skate retina. 2) The effects of neurotransmitters and their analogues on retinal neurons in amphibians and fish. 3) The origin and functional significance of the electroretinogram oscillatory potentials. 4) The synaptic organization of intracellularly-stained neurons.